Magnetic bias film and magnetic sensor using the same

ABSTRACT

A magnetic bias film  9  includes a magnetic bias magnet  11  that has magnetic layers and generates a magnetic field within a plane perpendicular to a lamination direction of the magnetic layers, which is manufactured in the shape of substantially a rectangular prism having a long side, a short side, and a thickness (in the lamination direction) in order of decreasing lengths. A ratio of the long side with respect to the short side of the magnetic bias magnet  11  in length is in a range of 5 to 200.

This is a 371 national phase application of PCT/JP04/13266 filed 06 Sep.2004, which claims priority to Japanese Patent Application No.2003-313945 filed 05 Sep. 2003, and Japanese Patent Application No.2004-000074 filed 05 Jan. 2004, the contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a magnetic bias film used in variouselectronic devices and a magnetic sensor using the same.

BACKGROUND ART

A magnetic sensor in the related art is disclosed, for example, inJP-A-2003-14458. FIG. 19 is a perspective view showing a magnetic sensorin the related art. FIG. 20 is a cross section taken along the lineII-II′ of the magnetic sensor in the related art shown in FIG. 19.

The magnetic sensor is of a configuration including a Wheatstone bridgecircuit 3 comprising four detecting elements 2A through 2D provided onthe top surface of a substrate 1, a holder 4 holding the substrate 1 tocover the substrate 1 having the Wheatstone bridge circuit, and a firstcoil 5A and a second coil 5B comprising conductive wires wound aroundthe holder 4 a specific number of turns and applying magnetic biasesthat are orthogonal to each other.

Because this magnetic sensor uses the first coil 5A and the second coil5B wound around the holder 4 as means for applying magnetic biases, itis increased in size and a reduction in size cannot be readily achieved.Also, in order to generate magnetic fields, it is necessary to flow acurrent through each of the first coil 5A and the second coil 5B, andpower consumption is consequently increased.

Also, for example, WO 03/056276 discloses a method of using magneticbias films formed of a thin film of magnet as means for applyingmagnetic biases.

This magnetic sensor can solve the problem discussed above because itdoes not use coils but it uses magnetic bias films formed ofsubstantially a square thin film of magnet when viewed in plan as meansfor applying magnetic biases.

In order to further reduce the magnetic sensor in size, the magneticbias film has to be reduced in size as well. To this end, it isnecessary to make the bottom area of the magnetic bias film smaller.

In this case, however, a magnetic field generated by the magnetic biasfilm becomes smaller, and there arises a problem that a desired magneticfield cannot be obtained. Further, when a large magnetic field isapplied to such a magnetic bias film from the outside, the orientationof the magnetic bias is affected, and there arises a problem that anoutput of the magnetic sensor is affected.

DISCLOSURE OF THE INVENTION

The invention solves the problems of the magnetic bias film in therelated art as discussed above, and therefore has an object to provide amagnetic bias film that can be reduced in size and is capable ofobtaining a stable and desired magnetic field and a magnetic sensorusing the same.

In order to achieve the above and other objects, a magnetic bias filmaccording to one aspect of the invention is a magnetic bias filmincluding plural magnetic bias magnets each having magnetic layers andgenerating a magnetic field within a plane perpendicular to a laminationdirection of the magnetic layers, and characterized in that the magneticbias magnet is manufactured in a shape of substantially a rectangularprism having a long side, a short side, and a thickness in thelamination direction in order of decreasing lengths while a ratio of thelong side with respect to the short side in length is in a range of 5 to200, and the plural magnetic bias magnets are disposed in a short sidedirection.

In order to achieve the above and other objects, a magnetic bias filmaccording to one aspect of the invention is a magnetic bias filmincluding a magnetic bias magnet that has magnetic layers and generatesa magnetic field within a plane perpendicular to a lamination directionof the magnetic layers, and characterized in that the magnetic biasmagnet is manufactured in a shape of substantially a rectangular prismhaving a long side, a short side, and a thickness in the laminationdirection in order of decreasing lengths while a ratio of the long sidewith respect to the short side in length is in a range of 5 to 200.

According to this configuration, the magnetic bias film of the inventionincludes the magnetic bias magnets, each of which is manufactured in theshape of substantially a rectangular prism having the long side, theshort side, and the thickness in the lamination direction in order ofdecreasing lengths. The ratio of the long side with respect to the shortside in length of the magnetic bias magnet is in a range of 5 to 200,and the plural magnetic bias magnets are disposed in the short sidedirection. The direction of a magnetic field generated within the planeperpendicular to the lamination direction of the magnetic layerscontained in the magnetic bias magnet is therefore stabilized, and astronger magnetic field can be obtained. Hence, not only can themagnetic bias film be reduced in size, but also the magnetic sensorusing the same can be reduced in size at the same time.

A magnetic sensor according to another aspect of the invention is amagnetic sensor, characterized by including: a substrate; a firstmagnetic detection portion provided with at least two magnetic detectingelements formed on a main surface side of the substrate; a secondmagnetic detection portion provided with at least two magnetic detectingelements formed on the main surface side of the substrate; a firstmagnetic bias film provided at a position opposing the first magneticdetection portion; and a second magnetic bias film provided at aposition opposing the second magnetic detection portion, wherein thefirst and second magnetic bias films are the magnetic bias filmaccording to any of claims 1 through 13, and an orientation of amagnetic field generated by the first magnetic bias film and anorientation of a magnetic field generated by the second magnetic biasfilm are different.

According to this configuration, in the magnetic sensor of theinvention, the first and second magnetic detection portions, each havingat least two magnetic detecting elements, are formed on the main surfaceside of the substrate. The first magnetic bias film is provided at aposition opposing the first magnetic detection portion, and the secondmagnetic bias film is provided at a position opposing the secondmagnetic detection portion. It is thus possible to apply the magneticbiases to the magnetic detection portions effectively.

Also, the orientations of the magnetic fields generated by the firstmagnetic bias film and the second magnetic bias film are different. Thisgives rise to a phase difference between output waveforms from the firstand second magnetic detection portions. Hence, by detecting a ratio ofthese two waveform outputs, it is possible to obtain a magnetic sensorof a simple configuration capable of detecting the direction of anexternal magnetic field.

The objects, features, aspects, and advantages of the invention willbecome more apparent by the following detailed descriptions and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a magnetic bias film according to a firstembodiment of the invention.

FIG. 2 is a longitudinal cross section of a magnetic bias magnet formingthe magnetic bias film according to the first embodiment of theinvention.

FIG. 3 is a perspective view of a magnetic bias film according to asecond embodiment of the invention.

FIG. 4 is a view showing the relation of a film thickness andmagnetization in a magnetic bias film in the related art and in themagnetic bias film according to the second embodiment of the invention.

FIG. 5 is a longitudinal cross section of a magnetic bias film of asingle-layer structure in the related art.

FIG. 6 is a longitudinal cross section of the magnetic bias filmaccording to the second embodiment of the invention.

FIG. 7 is a perspective view of a magnetic bias film according to athird embodiment of the invention.

FIG. 8 is a top view of the magnetic bias film according to the thirdembodiment of the invention.

FIG. 9 is a longitudinal cross section of the magnetic bias filmaccording to the third embodiment of the invention.

FIG. 10 is a perspective view of a magnetic sensor according to a fourthembodiment of the invention.

FIG. 11 is an exploded perspective view of the magnetic sensor accordingto the fourth embodiment of the invention.

FIG. 12 is a cross section taken along the line I-I′ of the magneticsensor according to the fourth embodiment of the invention.

FIG. 13 is a top view of first and second magnetic detection portions inthe magnetic sensor according to the fourth embodiment of the invention.

FIG. 14 is a circuit diagram of a first magnetic detection portion inthe magnetic sensor according to the fourth embodiment of the invention.

FIG. 15 is a view showing the relation of the bias magnetic fieldstrength and an orientation variation in the magnetic sensor accordingto the fourth embodiment of the invention.

FIG. 16 is a cross section showing a modification of the magnetic sensoraccording to the fourth embodiment of the invention.

FIG. 17 is a cross section of a magnetic sensor according to a fifthembodiment of the invention.

FIG. 18 is a circuit diagram showing a modification of a magneticdetection portion in the magnetic sensor according to the fifthembodiment of the invention.

FIG. 19 is a perspective view of a magnetic sensor in the related art.

FIG. 20 is a cross section taken along the line II-II′ of the magneticsensor in the related art.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the invention will be described withreference to the drawings. First through third embodiments below willdescribe magnetic bias films with which the direction of a magneticfield is stabilized by changing the shape or the configuration. Fourthand fifth embodiments will describe a magnetic sensor using thesemagnetic bias films.

Initially, in the first embodiment, the direction of a magnetic field isstabilized by manufacturing a magnetic bias film of a single-layerstructure in the shape of a rectangular prism. The second embodiment isdifferent from the first embodiment, and will describe a magnetic biasfilm of a laminated structure. The third embodiment will describe aconfiguration as a combination of the first and second embodiments, thatis, an example to stabilize the direction of a magnetic field bymanufacturing a magnetic bias film of a laminated structure in the shapeof a rectangular prism.

First Embodiment

FIG. 1 is a top view of a magnetic bias film according to a firstembodiment of the invention. This magnetic bias film 9 comprises pluralmagnetic bias magnets 9A through 9G, and each of these magnetic biasmagnets 9A through 9G generates a magnetic field in a directionindicated by an arrow A (x direction).

The magnetic bias magnets 9A through 9G are made of CoPt alloy in theshape of substantially a rectangular prism having a long side, a shortside, and a thickness (lamination direction) in order of decreasinglengths. Herein, the term, “substantially” a rectangular prism, is usedto include not only a mathematically perfect rectangular prism, but alsothose having, for example, warping, roundness or chamfers on the edgesor the apexes, or irregularities on the surface due to restrictions ofmanufacturing techniques, but deemed as being in the shape of arectangular prism as a whole. The concept includes magnetic bias magnets9A through 9G in the shape of a square cone platform having the bottomarea larger than the top area and inclined side surfaces due torestrictions of manufacturing techniques. This applies to all theembodiments below.

Also, CoPt alloy has large magnetocrystalline anisotropy in addition toan excellent magnet property. It is therefore preferable as a materialof the magnetic bias magnet to which the stability of the magnetic fielddirection is required.

In this case, the long side, the short side, and the thickness aredefined as follows using the coordinate axes shown in FIG. 1. That is, adirection perpendicular to the sheet surface (z direction) correspondsto the thickness direction, the x direction of the rectangle shown inFIG. 1 corresponds to the long side, and the y direction corresponds tothe short side. As to the respective sides in this embodiment, thelength of the long side is 700 μm, the length of the short side is 140μm, and the thickness is 2000 Å (=0.2 μm). An interval among themagnetic bias magnets 9A through 9G is 10 μm.

A ratio of the long side with respect to the short side in length(=length of long side/length of short side) of the magnetic bias magnet9A, that is, the aspect ratio, is 700 μm/140 μm=5. Hence, the magneticbias magnet 9A within the sheet surface is of a rectangular shape, andmagnetic shape anisotropy is provided in the long side direction (xdirection).

Also, the aspect ratio of the long side with respect to the thickness(=length of long side/thickness) of the magnetic bias magnet 9A is 700μm/0.2 μm=3500. Further, the aspect ratio of the short side with respectto the thickness (=length of short side/thickness) of the magnetic biasmagnet 9A is 140 μm/0.2 μm=700.

The other magnetic bias magnets 9B through 9G are of the sameconfiguration as the magnetic bias magnet 9A, and they are arrayed inthe lateral direction while the magnetic field directions are aligned.These magnetic bias magnets 9A through 9G together constitute a magneticbias film 9.

A manufacturing method of the magnetic bias film 9 configured asdescribed above will now be described.

Initially, a CoPt film is formed across the entire surface of asubstrate or the like by means of vapor deposition or sputtering. TheCoPt film is then divided by means of exposure, etching, or the like toobtain plural CoPt films in the shape of substantially a rectangularprism. By applying a specific magnetic field to these plural CoPt filmsin the shape of substantially a rectangular prim in the long sidedirection (x direction), the CoPt films in the shape of substantially arectangular prism are magnetized in the long side direction. Themagnetic bias magnets 9A through 9G can be thus obtained.

The magnetic bias film 9 of such a configuration seldom changes themagnetization direction upon application of a large magnetic field fromthe outside. The reason why is not completely explained logically;however, the reason why is roughly thought as follows.

FIG. 2 is a longitudinal cross section (the cross section on the x-zplane of FIG. 1) of the magnetic bias magnet forming the magnetic biasfilm 9 according to the first embodiment of the invention. Crystalgrains 10 are present within the magnetic bias magnets 9A through 9G. Asis shown in FIG. 2, the crystal grains 10 are thought to be ofsubstantially an elliptical shape having the long axis in the long sidedirection (x direction) of the magnetic bias magnets 9A through 9G. Themagnetic moment present within the crystal grain 10 is readily orientedin a direction indicated by an arrow B as a whole, and the direction ofthe magnetic moment hardly changes even when a large magnetic field isapplied from the outside.

In this case, the reason why the crystal grain 10 takes on substantiallyan elliptical shape is not clear. However, it is assumed that by makingthe magnetic bias magnets 9A through 9G in a markedly flattenedrectangular shape by setting the aspect ratio of the long side and theshort side to 5 or greater instead of making them in a square shape whenviewed in plan, the crystal grains 10 take on substantially anelliptical shape at the time of film deposition or polarization.

Further, influences of a so-called demagnetizing field that depend onthe shape (the aspect ratio of the long side and the short side) of themagnetic bias magnets 9A through 9G are thought to be present to nosmall extent. Generally, the (effective) magnetic field exerting withina magnetic body becomes smaller in magnitude comparable to thedemagnetizing field due to the magnetic field applied from the outside.The magnitude of the demagnetizing field is proportional to themagnitude of the magnetization of the magnetic body, and a proportionalfactor is referred to as a demagnetizing factor.

Given the shape of the magnetic bias magnet 9A used in this embodimentas an example by ignoring the thickness, then the demagnetizing factorin the long side direction (x direction) is small whereas thedemagnetizing factor in the short side direction (y direction) is large.Hence, the effective field in the long side direction becomes largewhereas the effective field in the short side direction becomes small.It is thus understood that the magnetization in the long side directionhaving a large effective field is more stable.

The aspect ratio of the long side and the short side of the magneticbias magnets 9A through 9G is preferably in a range of 5 to 200, andmore preferably in a range of 10 to 200. That is to say, when the aspectratio of the long side and the short side of the magnetic bias magnets9A through 9G is smaller than 5, the stability of the bias magneticfields generated by the magnetic bias magnets 9A through 9G isdeteriorated when a large magnetic field is applied from the outside.This can be understood from the view point of the demagnetizing fielddescribed above.

Meanwhile, when the aspect ratio of the long side and the short side ofthe magnetic bias magnets 9A through 9G is larger than 200, the absolutestrength of the bias magnetic fields generated by the magnetic biasmagnets 9A through 9G becomes too large to obtain the most appropriatebias magnetic field. Conversely, when the bias magnetic field isweakened while keeping the aspect ratio intact, manufacturing becomesdifficult because of a short length of the short side.

The aspect ratio of the long side and the short side of the magneticbias magnet 9A is set in a range of 5 to 200 for these reasons, and whenset in this range, the bias magnetic field generated by the magneticbias magnet 9A can be stabilized.

As has been described, when the crystal grains 10 are not of a circularshape when viewed in plan but of an anisotropic shape, which issubstantially an elliptical shape having the long axis in the long sidedirection of the magnetic bias magnet 9A, a bias magnetic field thatremains stable against a magnetic field from the outside is thought togenerate.

The direction of the long axis of the crystal grains 10 of substantiallyan elliptical shape is also a direction perpendicular to the thicknessdirection. The reason why for this configuration is thought to be thesame as the reason why the long axis of substantially an ellipticalshape is readily oriented in the long side direction due to the aspectratio of the long side and the short side, because the length of themagnetic bias magnet 9A in the thickness direction is shorter than thelengths in the long side and short side directions. Also with the aid ofthis configuration, the magnetic bias magnet 9A seldom changes themagnetization direction even when a large magnetic field is applied fromthe outside.

As the magnetic bias film according to the first embodiment of theinvention described above, the magnetic bias film 9 is formed byarraying the plural magnetic bias magnets 9A through 9D, each of whichgenerates a magnetic field and is in the shape of substantially arectangular prism having the long side, the short side, and thethickness in order of decreasing lengths, in a lateral direction whilealigning the directions of the magnetic fields. Further, because theaspect ratio of the long side and the short side of all the magneticbias magnets 9A through 9G is set in a range of 5 to 200, themagnetization direction seldom changes even when a large magnetic fieldis applied from the outside. It is thus possible to generate a stablemagnetic bias.

In addition, the thickness of the magnetic bias film 9 is preferably ina range of 250 Å to 2500 Å. When the thickness of the magnetic bias film9 is smaller than 250 Å, the magnetic field generated by a magneticlayer 12 becomes smaller. Meanwhile, the strength of the magnetic fieldhardly changes by making the thickness of the magnetic bias film 9larger than 2500 Å. It is therefore preferable to set the thickness ofthe magnetic bias film 9 in a range of 250 Å to 2500 Å.

Further, the magnetic bias magnets 9A through 9G may be formed in adivided state from the start instead of using the method for obtainingthe magnetic bias magnets 9A through 9G by forming a large CoPt filmfirst and then dividing the film by means of etching. In this case, theCoPt film is formed using a mask having the shapes of the magnetic biasmagnets 9A through 9G.

Second Embodiment

FIG. 3 is a perspective view of a magnetic bias film according to asecond embodiment of the invention. Referring to FIG. 3, a magnetic biasfilm 11 has a structure in which plural magnetic layers 12 andnon-magnetic layers 13 are laminated alternately. The magnetic layer 12is made of CoPt alloy, and generates a magnetic field in a directionindicated by an arrow A (x direction) when magnetized in a certaindirection. Also, the non-magnetic layer 13 is made of Cr. Strictlyspeaking, Cr is an antiferromagnetic material and is not non-magnetic.However, because it is not a ferromagnetic material, the term,“non-magnetic”, is used for Cr.

As to the respective sides in this embodiment, the length of the longside (x direction) is 700 μm, the length of the short side (y direction)is 140 μm, and the thicknesses (z direction) of the magnetic layer 12and the non-magnetic layer 13 are 2000 Å and 250 Å, respectively. Theaspect ratio of the long side with respect to the short side of themagnetic bias film 11 is 700 ml/140 μm=5. The magnetic bias film 11within the sheet surface is therefore of a rectangular shape, andmagnetic shape anisotropy is provided in the long side direction (xdirection).

Also, the aspect ratio of the long side with respect to the thickness(=length of long side/thickness) of the magnetic layer 12 is 700 μm/0.2μm=3500. Further, the aspect ratio of the short side with respect to thethickness (=length of short side/thickness) of the magnetic layer 12 is140 μm/0.2=700.

In this embodiment, because there is a single magnetic bias magnet, itis equivalent to the magnetic bias film.

A manufacturing method of the magnetic bias film 11 configured asdescribed above will now be described. The magnetic layer 12 made ofCoPt alloy is formed on the surface of a substrate (not shown) by meansof vapor deposition or sputtering, and the non-magnetic layer 13 made ofCr is formed on the top surface of this magnetic layer 12 by means ofvapor deposition or sputtering. Further, the magnetic layer 12 is formedon the top surface of this non-magnetic layer 13, and by repeating theseprocedures, it is possible to obtain a laminated film in which pluralmagnetic layers 12 and non-magnetic layers 13 are laminated in the zdirection.

By applying a specific magnetic field in a certain direction (xdirection in FIG. 3) perpendicular to the lamination direction of thesemagnetic layers 12, the magnetic layers 12 in the laminated film aremagnetized in a direction (x direction) indicated by an arrow A. Themagnetic bias film 11 can be thus obtained.

The magnetic bias magnet 11 is not of substantially a square shape, andas in the first embodiment above, the aspect ratio of the short side (ydirection) and the long side (x direction) is preferably in a range of 5to 200, and more preferably in a range of 10 to 200. More specifically,when the aspect ratio of the long side and the short side of themagnetic bias magnet 11 is smaller than 5, the stability of the biasmagnetic field is deteriorated, and when the aspect ratio is larger than200, the absolute strength of the bias magnetic field becomes too large.

The magnetic bias film 11 of such a laminated structure is able togenerate a large magnetic field in comparison with a magnetic bias filmof a single-layer structure in which the film thickness of the magneticlayer is merely increased as in the magnetic bias film in the relatedart. This will be described with reference to the drawings.

FIG. 4 shows magnetic properties of the magnetic bias film of asingle-layer structure in the related art and the magnetic bias film ofa laminated structure in this embodiment. The abscissa is used for thefilm thickness of the magnetic layer indicated in units of A and theordinate is used for magnetization of the magnetic layer indicated inunits of emu.

Referring to FIG. 4, the results of the magnetic bias films of thelaminated structure and the single-layer structure are indicated byboxes (or tilted boxes), and these results are linked by a solid lineand a dotted line almost on straight lines. Herein, 2000 Å is given tothe single magnetic layer 12 in the magnetic bias film of the laminatedstructure. Hence, the thicknesses of 4000 Å, 6000 Å, and 8000 Å meanthat the magnetic bias film comprises two, three, and four magneticlayers 12, respectively. The non-magnetic layer 13 is interposed betweenthese magnetic layers 12.

As can be understood from FIG. 4, the magnitude of magnetization hardlychanges in the magnetic bias film of the single-layer structure in therelated art by increasing the film thickness. On the contrary,magnetization is increased with the film thickness in the magnetic biasfilm of the laminated structure of this embodiment. The reason why isnot completely explained logically; however, the reason why is roughlythought as follows.

FIG. 5 is a longitudinal cross section of the magnetic bias film of thesingle-layer structure in the related art. FIG. 6 is a longitudinalcross section of the magnetic bias film of the laminated structure inthis embodiment. Each of them is a cross section on the x-z plane ofFIG. 3.

Crystal grains 14 are present within a magnetic bias film 15 of thesingle-layer structure in the related art shown in FIG. 5. Also, theorientations of the magnetic moments of the crystal grains 14 areindicated by arrows inside the crystal grains 14.

As is shown in FIG. 5, the crystal grains 14 are thought to be ofsubstantially an elliptical shape, and the long axis directions of thecrystal grains 14 are present randomly within the magnetic bias film 15of a thin single-layer structure while being aligned relatively in thelong side direction (x direction). When the thickness of the magneticbias film 15 of the single-layer structure is merely increased, thenumber of the crystal grains 14 present within is increasedcorrespondingly. However, the long axis directions of the crystal grains14 are oriented not only in the long side directions but also in thethickness direction (z direction) perpendicular to the long sidedirections.

In this case, the magnetic bias film 15 of the single-layer structure inthe related art as a whole generates a magnetic field in the long sidedirection of the magnetic bias film 15 of the single-layer structure.However, the magnetic moments of the respective crystal grains 14 havealso a component in the thickness direction of the magnetic bias film 15of the single-layer structure. The magnetic field component in thethickness direction does not contribute to the strength of the magneticfield in the long side direction of the magnetic bias film 15 of thesingle-layer structure. It is therefore thought that the components inthe thickness direction that the magnetic moments of the crystal grains14 have are increased as the thickness of the magnetic bias film 15 ofthe single-layer structure is increased. It is therefore thought thatthe magnetic field in the long side direction is not increasedcorrespondingly by merely increasing the thickness of the magnetic biasfilm 15 of the single-layer structure.

On the contrary, in the magnetic bias film 11 of the laminated structureof the invention shown in FIG. 6 having the configuration in which themagnetic layers 12 are laminated via the non-magnetic layers 13, therespective magnetic layers 12 are separated by the non-magnetic layers13. The orientation of the respective crystal grains 14 are thereforedominated by the thickness of the respective magnetic layers 12, and thelong axis directions of the crystal grains 14 are present while beingaligned relatively in the long side direction. This lessens thecomponents in the thickness direction of the magnetic moments of therespective crystal grains 14. The magnetic moments of the crystal grains14 are therefore thought to contribute to the strength of the magneticfield in the long side direction.

The orientations of the magnetic moments on the x axis shown in FIG. 6(either it is leftward or rightward in the drawing) are shownschematically, and it does not necessarily mean that all the magneticmoments are aligned in the same direction.

It is not clear why the crystal grains 14 take on substantially anelliptical shape. However, because the magnetic bias film 11 of thelaminated structure of the invention is of a flattened structure inwhich the film thickness of the magnetic layer 12 is particularly thinand the thickness direction with respect to the long side direction isextremely short, the crystal grains 14 are thought to take onsubstantially an elliptical shape oriented in the long side direction atthe time of film deposition or polarization.

Further, influences of the demagnetizing field that depend on the shapeof the magnetic bias film 11 are thought to be present to no smallextent. Assume that the lengths of the magnetic bias film 11 in thelateral direction (x direction) in FIG. 5 and FIG. 6 are equal byignoring the length in a direction (y direction) perpendicular to thesheet surface. That is, the magnetic bias film 11 of the single-layerstructure and the single magnetic layer 12 forming the laminatedstructure are different in length in the thickness direction (zdirection) alone.

In this instance, the demagnetizing factors in the thickness direction(z direction) of the magnetic bias films 11 of the single-layerstructure and the laminated structure are almost equal. On the contrary,the demagnetizing factor in the x direction is large in the single-layerstructure shown in FIG. 5 whereas it is small in the single magneticlayer 12 forming the laminated structure shown in FIG. 6. However, thevalue of the demagnetizing factor in the x direction of either structuretakes a vale smaller than the demagnetizing factor in the z direction.Hence, a difference between the values of the demagnetizing factors inthe x direction and the z direction is larger in the laminated structureshown in FIG. 6 than in the single-layer structure shown in FIG. 5.

That is to say, in the laminated structure shown in FIG. 6,magnetization in the x direction is stabilized, because the effectivefield in the lateral direction (x direction) in the sheet surface islarge and the effective field in the longitudinal direction (zdirection) in the sheet surface is small in comparison with the formereffective field. On the contrary, in the single-layer structure shown inFIG. 5, magnetization in the x direction becomes unstable, because adifference between the effective fields in the longitudinal direction (zdirection) and the lateral direction (x direction) on the sheet surfaceis small. The magnetization is thus readily oriented in the z direction(thickness direction).

The thickness of the magnetic layer 12 is preferably in a range of 250 Åto 2500 Å. When the thickness of the magnetic layer 12 is smaller than250 Å, a magnetic field generated by the magnetic layer 12 becomessmall. Meanwhile, even when the thickness of the magnetic layer 12 islarger than 2500 Å, as is shown in FIG. 5, the components in thethickness direction of the magnetic moments of the crystal grains 14 areincreased further, and the strength of the magnetic field hardlychanges. It is therefore preferable to set the thickness of the magneticlayer 12 in a range of 250 Å to 2500 Å.

Also, the thickness of the non-magnetic layer 13 is preferably in arange of 50 Å to 500 Å. Herein, when the thickness of the non-magneticlayer 13 is smaller than 50 Å, the magnetic layers 12 disposed above andbeneath the non-magnetic layer 13 may possibly interfere with each otherand give adverse influences. Meanwhile, when the thickness of thenon-magnetic layer 13 is larger than 500 Å, the entire thickness isundesirably increased. It is therefore preferable to set the thicknessof the non-magnetic layer 13 in a range of 50 Å to 500 Å.

The non-magnetic layers 13 forming the magnetic bias film 11 are notlimited to Cr as is described in this embodiment, and other non-magneticelements, such as Ti, Cu, Al, Sn, Nb, Au, Ag, Ta, and W can be used aswell.

Also, in a case where the magnetic layer 12 and the non-magnetic layer13 are formed to manufacture the magnetic bias film 11, the magneticlayer 12 and the non-magnetic layer 13 are formed on the surface of thesubstrate (not shown) by means of vapor deposition or sputtering in thesecond embodiment of the invention. The invention is not limited to thisformation method, and for example, the magnetic layer 12 and thenon-magnetic layer 13 may be formed by forming CoPt alloy and Cralternately plural times by a wet method. Alternatively, the magneticlayer 12 and the non-magnetic layer 13 may be formed by alternatelyapplying a CoPt precursor and a Cr precursor plural times by another wetmethod followed by sintering.

Further, because at least two magnetic layers 12 are necessary, it isdesirable to dispose the magnetic layers 12 at the uppermost layer andthe lowermost layer of the lamination to further reduce a totalthickness of the magnetic bias film 11.

As has been described, in the second embodiment of the invention,because the magnetic bias film 11 is formed by laminating pluralmagnetized magnetic layers 12 and non-magnetic layers 13, it is possibleto obtain the magnetic bias film 11 that generates a large magneticfield in response to the thickness of the magnetic layer 12.

Third Embodiment

FIG. 7 is a perspective view of a magnetic bias film according to athird embodiment of the invention. A magnetic bias film 11 according tothe third embodiment of the invention comprises plural magnetic biasmagnets 11A through 11C, and generates a magnetic field in a direction(x direction) indicated by an arrow A. The magnetic bias magnet 11A isof a structure in which plural magnetic layers 12 made of CoPt alloy andnon-magnetic layers 13 made of Cr are laminated, and it is in the shapeof substantially a rectangular prism having the long side (y direction),the short side (x direction), and the thickness (z direction), which isalso the lamination direction of the magnetic bias film 11A, in order ofdecreasing lengths.

As to the respective sides in this embodiment, the length of the longside (y direction) is 700 μm, the length of the short side (x direction)is 140 μm, and both intervals between the magnetic bias magnets 11A and11B and between the magnetic bias magnets 11B and 11C are 10 μm. Thethicknesses (z direction) of the magnetic layer 12 and the non-magneticlayer 13 are 2000 Å and 250 Å, respectively. The aspect ratio of thelong side with respect to the short side of the magnetic bias magnet 11Ais therefore 700 μm/140 μm=5.

Also, the aspect ratio of the long side with respect to the thickness ofthe magnetic layer 12 (=length of long side/thickness) is 700 ml/0.2μm=3500. Further, the aspect ratio of the short side with respect to thethickness of the magnetic layer 12 (=length of short side/thickness) is140 μm/0.2 μm=700.

The other magnetic bias magnets 11B and 11C are of the sameconfiguration as the magnetic bias magnet 11A, and these are arrayed inthe lateral direction of the drawing, that is, in the short sidedirection (x direction) of substantially a rectangular prism whilealigning the magnetic field directions. These magnetic bias magnets 11Athrough 11C together constitute the magnetic bias film 11.

Herein, the aspect ratio of the short side (x direction) and the longside (y direction) of the magnetic bias magnets 11A through 11C ispreferably in a range of 5 to 200, and more preferably in a range of 10to 200 as in the first and second embodiments above. To be morespecific, this is because when the aspect ratio of the long side and theshort side of the magnetic bias magnets 11A through 11C is smaller than5, the stability of the bias magnetic field is deteriorated, and whenthe aspect ratio is larger than 200, the absolute strength of the biasmagnetic field becomes too large.

A manufacturing method of the magnetic bias film 11 according to thethird embodiment of the invention configured as described above will nowbe described.

The magnetic layer 12 made of CoPt alloy is formed on the surface of asubstrate (not shown) by means of vapor deposition or sputtering, andthe non-magnetic layer 13 made of Cr is formed on the top surface ofthis magnetic layer 12 by means of vapor deposition or sputtering.Further, the magnetic layer 12 is formed on the top surface of thenon-magnetic layer 13, and by repeating these procedures, it is possibleto obtain a laminated film in which plural magnetic layers 12 andnon-magnetic layers 13 are laminated.

After resist is applied, the patterning using the photolithographictechnique is performed by means of exposure and development, and thenthe laminated film is divided by means of etching. Plural laminatedfilms in the shape of substantially a rectangular prism can be thusobtained.

In these plural laminated films in the shape of substantially arectangular prism, by applying a specific magnetic field in the longside direction or the short side direction, it is possible to obtain themagnetic bias magnets 11A through 11C in which the magnetic layers inthe laminated film in the shape of substantially a rectangular prism aremagnetized in the long side direction or the short side direction.

Also, in such a configuration, the magnetic bias film 11 is magnetizedmore readily in the short side direction than in the long sidedirection. More specifically, in the magnetic bias film 11 magnetized inthe short side direction, the magnetization direction hardly changeseven when a large magnetic field is applied from the outside incomparison with a case where it is magnetized in the long sidedirection. In other words, it is thought that large magnetic anisotropyis provided in the short side direction rather in the long sidedirection in this embodiment. This state will be described withreference to FIG. 8.

FIG. 8 is a top view of the magnetic bias film 11 according to the thirdembodiment of the invention. Herein, the magnetic layers 12 aremagnetized in the short side direction (x direction) of the magneticbias magnets 11A through 11C. In this case, a magnetic bias that remainsstable against the external magnetic field can be generated by disposingthe magnetic moments in the short side direction (x direction) ratherthan disposing the magnetic moments in the long side direction (ydirection). The reason why is not clearly explained logically. However,interactions among the magnetic bias magnets 11A through 11C andinteractions among the respective magnetic layers 12 caused bylaminating plural magnetic layers 12 are thought to be involved.

FIG. 9 is a longitudinal cross section (the cross section on the x-zplane of FIG. 7) of the magnetic bias film of the laminated structure inthis embodiment. In this embodiment, of the three magnetic layers 12,the orientation of magnetization of the magnetic layer 12 in the middleis thought to be reversed to the orientation of the magnetization of theother magnetic layers due to magnetostatic coupling among the magneticlayers 12. It is therefore preferable to laminate an odd number ofmagnetic layers 12 in the magnetic bias film of this embodiment. This isbecause the magnetic bias film 11 having properties that remain stableagainst a magnetic field from the outside can be obtained whenconfigured in this manner.

Also, in the third embodiment of this invention, there is an effectachieved from the configuration in which the magnetic layers 12 arelaminated by interposing the non-magnetic layer 13 in between as hasbeen described in the second embodiment of the invention. In short,there is an effect that the magnetic field becomes stronger with anincreasing number of the magnetic layers 12.

As has been described, in the magnetic bias film 11 according to thethird embodiment of the invention, the magnetic bias magnets 11A through11C, each of which is in the shape of substantially a rectangular prismformed by laminating plural magnetic layers 12 and non-magnetic layers13 alternately, are arrayed in the short side direction of substantiallya rectangular prism. Also, because the aspect ratio of the short sideand the long side is set in a range of 5 to 200 for these magnetic biasmagnets 11A through 11C, it is possible to obtain a strong magneticfield in comparison with the single-layer magnetic bias film in therelated art. This provides effects that not only can the magnetic biasfilm be reduced in size, but also a magnetic field that remains stableagainst an external magnetic field can be obtained.

Also, as to the thickness of the magnetic layer 12 and the thickness ofthe non-magnetic layer 13 in the third embodiment of the invention, itis preferable to set the thickness of the magnetic layer 12 in a rangeof 250 Å to 2500 Å, and it is preferable to set the thickness of thenon-magnetic layer 13 in a range of 50 Å to 500 Å as in the secondembodiment of the invention described above.

The non-magnetic layers 13 forming the magnetic bias film 11 is notlimited to Cr as described in the third embodiment of the invention, andother non-magnetic elements, such as Ti, Cu, Al, Sn, Nb, Au, Ag, Ta, andW, can be used as well.

The method of obtaining the magnetic bias magnets 11A through 11C is notlimited to the method of obtaining the magnetic bias magnets 11A through11C by forming a large laminated film of CoPt alloy and Cr first andthen dividing the film by means of etching as the manufacturing methodof the magnetic film in the third embodiment of the invention describedabove, and the magnetic bias magnets 11A through 11C may be formed in adivided state from the start. In this case, a laminated film of CoPtalloy and Cr is formed using a mask having the shapes of the magneticbias magnets 11A through 11C.

Fourth Embodiment

FIG. 10 is a perspective view of a magnetic sensor according to a fourthembodiment of the invention. FIG. 11 is an exploded perspective view ofthe magnetic sensor. FIG. 12 is a cross section taken along the lineI-I′ of FIG. 10. FIG. 13 is a top view of first and second magneticdetection portions in the magnetic sensor. FIG. 14 is a circuit diagramof the first magnetic detection portion in the magnetic sensor.

Referring to FIG. 10 through FIG. 14, it is preferable that a substrate20 is made of a material having an insulation property, such as alumina,and that a glass glazed layer (not shown) is formed on the top surface(main surface). The glass glazed layer is used because not only can asmooth surface be readily obtained, but also first and second magneticdetection portions 21 and 22 can be formed on its top surface with ease.

In this embodiment, each of the first magnetic detection portion 21 andthe second detection portion 22 comprises four magnetic detectingelements. The magnetic detecting element is an element that outputs asignal in response to the orientation and magnitude of a magnetic fieldand is therefore used to detect the orientation of the magnetic field orthe like. Examples include an element using the magneto resistanceeffect (magneto resistance effect element), a Hall element, a magnetoimpedance effect element, etc.

These magnetic detecting elements are formed of a magneto resistancefilm formed on the top surface of the substrate 20. The magnetoresistance film is formed of a magnetic film, such as a ferromagneticthin film including NiCo or NiFe, and an artificial latticed multi-layerfilm. The first and second magnetic detection portions 21 and 22 reachthe maximum amount of change in resistance when an external magneticfield is applied perpendicularly to the surface on which they areformed.

Also, the magneto resistance film forming the first and second magneticdetection portions 21 and 22 is formed by being folded plural times.This is because the number of lines crossing magnetism (for example,earth magnetism) that needs to be measured is increased by being foldedplural times, and an amount of change in resistance is increased, whichcan in turn enhance the detection sensitivity.

A first insulation layer 23A is made of SiO₂ having an insulationproperty, and covers the first magnetic detection portion 21 toelectrically isolate the first magnetic detection portion 21 from afirst magnetic bias film 24 described below. As with the firstinsulation layer 23A, a second insulation layer 23B is also made of SiO₂having an insulation property, and covers the second magnetic detectionportion 22 to electrically isolate the second magnetic detection portion22 from a second magnetic bias film 25 described below.

The first magnetic bias film 24 is formed on the top surface of thefirst insulation layer 23A and applies a magnetic bias to the firstmagnetic detection portion 21. The first magnetic bias film 24 is themagnetic bias film 11 described in the third embodiment of the inventionabove, that is, the magnetic bias film 11 that comprises the magneticbias magnets 11A through 11C, in each of which plural magnetic layers 12made of CoPt alloy and magnetized in one direction and pluralnon-magnetic layers 13 made of Cr are laminated alternately while theaspect ratio of the short side and the long side is set in a range of 5to 200 by arraying the plural magnetic bias magnets 11A through 11C inthe short side direction to generate a magnetic field in the short sidedirection.

The second magnetic bias film 25 is formed on the top surface of thesecond insulation layer 23B and applies a magnetic bias to the secondmagnetic detection portion 22. The second magnetic bias film 25 alsouses the magnetic bias film 11 described in the third embodiment of theinvention above. The first and second magnetic bias films 24 and 25 havea large rate of change of resistance values in the first and secondmagnetic detection portions 21 and 22, and they are adjusted in such amanner that the resistance values change almost linearly in response toa change of the magnetic field.

A first covering layer 26A is made of epoxy resin, silicon resin, or thelike, and covers the first magnetic bias film 24. Likewise, a secondcovering layer 26B is made of epoxy resin, silicon resin, or the like,and covers the second magnetic bias film 25.

A first magnetic detecting element 27A and a second magnetic detectingelement 27B are electrically connected in series, and the longitudinaldirections of their patterns are different by 90°. Also, a thirdmagnetic detecting element 27C and a fourth magnetic detecting element27D are electrically connected in series, and the longitudinaldirections of their patterns are different by 90°. Further, the firstmagnetic detecting element 27A and the second magnetic detecting element27B are electrically connected to the third magnetic detecting element27C and the fourth magnetic detecting element 27D in parallel. Also, thelongitudinal directions of the patterns of the first magnetic detectingelement 27A and the third magnetic detecting element 27C are differentby 90°.

A first input electrode 28A is formed on the substrate 20, and iselectrically connected to the first magnetic detecting element 27A andto the third magnetic detecting element 27C. A first ground electrode29A is electrically connected to the second magnetic detecting element27B and to the fourth magnetic detecting element 27D. A first outputelectrode 30A is electrically connected to the first magnetic detectingelement 27A and to the second magnetic detecting element 27B, and asecond output electrode 30B is electrically connected to the thirdmagnetic detecting element 27C and to the fourth magnetic detectingelement 27D. Also, as with the first magnetic detection portion 21, thesecond magnetic detection portion 22 comprises a fifth magneticdetecting element 27E through an eighth magnetic detecting element 27H,a second input electrode 28B, a second ground electrode 29B, a thirdoutput electrode 30C, and a fourth output electrode 30D. Thesecomponents correspond, respectively, to the first magnetic detectingelement 27A through the fourth magnetic detecting element 27D, the firstinput electrode 28A, the first ground electrode 29A, the first outputelectrode 30A, and the second output electrode 30B in the first magneticdetection portion 21.

The first input electrode 28A and the second input electrode 28B areelectrically connected to each other, and the first ground electrode 29Aand the second ground electrode 29B are also electrically connected toeach other. The first magnetic detection portion 21 and the secondmagnetic detection portion 22 are therefore electrically connected inparallel. Also, the first input electrode 28A, the second inputelectrode 28B, the first ground electrode 29A, the second groundelectrode 29B, and the first output electrode 30A through the fourthoutput electrode 30D are made of silver or silver palladium.

Each of the first magnetic detecting element 27A through the fourthmagnetic detecting element 27D that together form the first magneticdetection portion 21 is formed of a magneto resistance film, and as isshown in FIG. 14, they constitute a Wheatstone bridge circuit as awhole. Hence, a difference between two output voltages (differentialoutput voltage) obtained from the first output electrode 30A and thesecond output electrode 30B becomes larger, which enables theorientation to be detected with accuracy. Further, because noises of thetwo output voltages can be canceled, it is possible to suppressdetection variations caused by noises.

A magnetic field 31 in FIG. 13 specifies the direction of a magneticfield that the first magnetic bias film 24 applies to the first magneticdetection portion 21. Meanwhile, a magnetic field 32 specifies thedirection of a magnetic field that the second magnetic bias film 25applies to the second magnetic detection portion 22, and this directionis different from that of the magnetic field 31 by 90°.

In this embodiment, it is configured in such a manner that an angleproduced by the magnetic fields generated by the first and secondmagnetic bias films 24 and 25 and the longitudinal directions of therespective patterns of the first magnetic detecting element 27A throughthe eighth magnetic detecting element 27H is 45°. The magnetic fieldsgenerated by the first and second magnetic bias films 24 and 25 at theangle of 0° or 180° do not contribute to a change in resistance of thefirst through eighth magnetic detecting elements 27A through 27H, andtherefore they do not play a role of the bias magnetic fields. Hence,the angle may be other than 45°; however, it is preferable to excludeangles of 0° and 180°.

A manufacturing method of the magnetic sensor according to the fourthembodiment of the invention configured as described above will now bedescribed.

Initially, the first magnetic detecting element 27A through the eighthmagnetic detecting elements 27H, the first input electrode 28A, thesecond input electrode 28B, the first ground electrode 29A, the secondground electrode 29B, the first output electrode 30A, the second outputelectrode 30B, the third output electrode 30C, and the fourth outputelectrode 30D are formed on the top surface of the substrate 20 by meansof printing, vapor deposition, or the like.

In this instance, the first magnetic detection portion 21 comprising thefirst magnetic detecting element 27A through the fourth magneticdetecting element 27D is formed, while the first input electrode 28A,the first ground electrode 29A, the first output electrode 30A, and thesecond output electrode 30B are formed at their specific positions.Likewise, the second magnetic detection portion 22 comprising the fifthmagnetic detecting element 27E through the eighth magnetic detectingelement 27H is formed, while the second input electrode 28B, the secondground electrode 29B, the third output electrode 30C, and the fourthoutput electrode 30D are formed at their specific positions.

Subsequently, the first insulation layer 23A is formed on the topsurface of the first magnetic detection portion 21, and the secondinsulation layer 23B is formed on the top surface of the second magneticdetection portion 22. In this instance, the first insulation layer 23Ais formed to cover at least the first magnetic detecting element 27Athrough the fourth magnetic detecting element 27D, and the secondinsulation layer 23B is formed to cover at least the fifth magneticdetecting element 27E through the eighth magnetic detecting element 27H.

Subsequently, the first magnetic bias film 24 is formed on the topsurface of the first insulation layer 23A at a position opposing thefirst magnetic detection portion 21 by means of vapor deposition,sputtering, or the like, and the second magnetic bias film 25 is formedon the top surface of the second insulation layer 23B at a positionopposing the second magnetic detection portion 22 by means of vapordeposition, sputtering, or the like.

The orientations of the respective magnetic fields are then set bybringing a magnetic field generating coil into close proximity to thefirst magnetic bias film 24 and to the second magnetic bias film 25. Inthis instance, it is configured in such a manner that an angle producedby the magnetic fields generated by the first magnetic bias film 24 andthe second magnetic bias film 25 and the longitudinal directions of therespective patterns of the first magnetic detecting element 27A throughthe eighth magnetic detecting element 27H is 45°. In addition, it isconfigured in such a manner that the directions of the magnetic fieldsgenerated by the first magnetic bias film 24 and the second magneticbias film 25 are different from each other by approximately 90°.

Finally, the first covering layer 26A is formed on the top surface ofthe first magnetic bias film 24 by means of molding or the like, and thesecond covering film 26B is formed on the top surface of the secondmagnetic bias film 25 by means of molding or the like.

The magnetic sensor according to the fourth embodiment of the inventioncan be obtained by the manufacturing method described above.

When the first magnetic bias film 24 and the second magnetic bias film25 are formed by the lift-off method, there can be achieved an effectthat damages on the first insulation layer 23A and the second insulationlayer 23B or on the first magnetic detection portion 21 and the secondmagnetic detection portion 22 can be prevented. More specifically, itmay be configured in such a manner that after resist is applied to aportion where the first magnetic bias film 24 and the second magneticbias film 25 are not formed, the CoPt film is formed across the entiresurfaces of the first insulation layer 23A and the second insulationlayer 23B, and the first magnetic bias film 24 and the second magneticbias film 25 are formed at the specific positions by removing the resistlater.

In this case, the unwanted CoPt film can be removed simultaneously bymerely removing the resist, the need to remove the CoPt film directly asin the etching method can be eliminated. It is thus possible to preventan etching liquid or the like from adhering to or penetrating into thefirst insulation layer 23A and the second insulation layer 23B or thefirst magnetic detection portion 21 and the second magnetic detectionportion 22.

In particular, in a case where CoPt alloy is used for the first magneticbias film 24 and the second magnetic bias film 25, it is necessary touse a strongly acidic etching liquid. Hence, the etching liquid givesdamages as it adheres to or penetrates into the first insulation layer23A and the second insulation layer 23B or the first magnetic detectionportion 21 and the second magnetic detection portion 22, and maypossibly deteriorate the moisture resistance. The lift-off method,however, does not raise such a problem and a magnetic sensor as a highlyreliable orientation sensor can be obtained.

Also, by setting the orientations of the magnetic fields after the firstmagnetic bias film 24 and the second magnetic bias film 25 are formed,it is possible to set the orientations of the magnetic fields generatedby the first magnetic bias film 24 and the second magnetic bias film 25simultaneously or in succession. The productivity can be thereforeenhanced.

Alternatively, magnetic thin films in which the orientation of themagnetic field has been previously set may be disposed on the topsurface of the first insulation layer 23A and the second insulationlayer 23B.

Operations of the magnetic sensor according to the fourth embodiment ofthe invention will now be described.

Referring to FIG. 10 through FIG. 14, when a specific voltage is appliedbetween the first input electrode 28A and the first ground electrode 29Ain the first magnetic detection portion 21, a change in resistance inresponse to the direction of the earth magnetization is caused in thefirst magnetic detecting element 27A through the fourth magneticdetecting element 27D. Because voltages in response to the change of theresistance value are outputted consequently from the first outputelectrode 30A and the second output electrode 30B, it is possible todetect a differential output voltage between these electrodes. Thedifferential output voltage changes with an angle at which the earthmagnetization crosses with the first magnetic detection portion 21, andit shapes substantially a sine wave by rotating the orientation of theearth magnetization by 360°.

As with the description above, by applying a specific voltage betweenthe second input electrode 28B and the second ground electrode 29B inthe second magnetic detection portion 22, a change in resistance inresponse to the direction of the earth magnetization is caused in thefifth magnetic detecting element 27E through the eighth magneticdetecting element 27H. Because voltages in response to a change of theresistance value are outputted consequently from the third outputelectrode 30C and the fourth output electrode 30D, it is possible todetect a differential output voltage between these electrodes. As withthe description above, this differential output voltage also changeswith an angle at which the earth magnetization crosses with the secondmagnetic detection portion 15, and it shapes substantially a sine waveby rotating the direction of the earth magnetization by 360°.

By making the magnetic field directions between the first magnetic biasfilm 24 and the second magnetic bias film 25 different by 90° as in thisembodiment, the phases of one differential output voltage and the otherdifferential output voltage are shifted by 90°. More specifically, givenθ as the orientation in reference to a specific one direction, then, ina case where one differential output voltage is Asinθ, the otherdifferential output voltage is Acosθ. Because a ratio of these twooutputs is tanθ, the orientation θ can be readily detected.

The bias magnetic field strengths of the first magnetic bias film 24 andthe second magnetic bias film 25 will now be described.

FIG. 15 is a view showing the relation of the bias magnetic fieldstrength of the magnetic sensor and an orientation variation in thisembodiment. Because the orientation variation that the magnetic sensordetects is increased when the bias magnetic field strength becomes toostrong or too weak, appropriate strength has to be set. An allowablevariation of the orientation to detect 36 orientations is thought to be7°. For the bias magnetic field in this case, 5 to 20 Oe is suitable ascan be understood from FIG. 15.

When a required orientation variation is made smaller, the strength ofthe bias magnetic field is limited further. For example, when anallowable variation of the orientation is 5°, the bias magnetic field islimited to 6 to 18 Oe, and more preferably, the bias magnetic field islimited to 7.5 to 15 Oe.

In the magnetic sensor in this embodiment described above, as the firstand second magnetic bias films 24 and 25 that apply magnetic biases,respectively, to the first and second magnetic detection portions 21 and22 having the magneto resistance effect, the magnetic bias film 11 isused, which is formed by arraying the magnetic bias magnets 11A through11C, each of which is in the shape of substantially a rectangular prismand formed by laminating plural magnetic layers 12 and non-magneticlayers 13 alternately while the aspect ratio of the short side and thelong side is set in a range of 5 to 200, in the short side direction togenerate a magnetic field in the short side direction. A total filmthickness of the magnetic bias film 11 can be therefore smaller, and astable magnetic bias can be obtained. It is thus possible to obtain amagnetic sensor that can be reduced in size and has properties thatremain stable against a magnetic field from the outside.

Also, the magnetic bias from the first magnetic bias film 24 is appliedto the first magnetic detection portion 21, while the magnetic bias fromthe second magnetic bias film 25 is applied to the second magneticdetection portion 22. By making the directions of the magnetic fieldgenerated by the first magnetic bias film 24 and the magnetic fieldgenerated by the second magnetic bias film 25 different, it is possibleto obtain a compact, high-sensitive magnetic sensor suitable todetection of the direction of earth magnetization.

In particular, because it is configured in such a manner that directionsof the magnetic field generated by the first magnetic bias film 24 andthe magnetic field generated by the second magnetic bias film 25 aredifferent by 90°, an output waveform from the first magnetic detectionportion 21 and an output waveform from the second magnetic detectionportion 22 have a phase difference of 90°. By finding a ratio of thesetwo waveform outputs, it is possible to obtain a magnetic sensor of asimple configuration capable of detecting the direction of an externalmagnetic field.

It goes without saying that the directions of the magnetic fieldgenerated by the first magnetic bias film 24 and the magnetic fieldgenerated by the second magnetic bias film 25 can be set to an angleother than 90°. In this case, the orientations of the magnetic fieldsgenerated by the first magnetic bias film 24 and the second magneticbias film 25 are made different so that the phases of the outputs fromthe first magnetic detection portion 21 and the second magneticdetection portion 22 differ from each other.

According to this configuration, because an output from the firstmagnetic detection portion 21 shapes a sine wave, it takes the samevalue at angles in two orientations; however, it is possible todetermine a single angle according to the sign of a difference betweenan output of the first magnetic detection portion 21 and an output ofthe second magnetic detection portion 22. All the orientations in arange of 0 to 360° can be therefore detected. In this instance, it isnecessary to make the orientations of the magnetic fields different tothe extent that the waveforms of the respective outputs of the firstmagnetic detection portion 21 and the second magnetic detection portion22 will not superimpose.

The magnetic sensor of the invention is not limited to the configurationof the magnetic sensor in this embodiment, and, for example, amodification as follows is possible.

FIG. 16 is a cross section showing a modification of the magnetic sensoraccording to the fourth embodiment of the invention. In the magneticsensor shown in FIG. 10 through FIG. 12, the insulation layer 23A andthe insulation layer 23B are separate, individual layers, and thecovering layer 26A and the covering layer 26B are also separate,individual layers. In the magnetic sensor shown in FIG. 16, however, itis configured in such a manner that an insulation layer 23 covers boththe first magnetic detection portion 21 and the second magneticdetection portion 22. Also, it is configured in such a manner that acovering layer 26 covers both the first magnetic bias film 24 and thesecond magnetic bias film 25. Even when configured in this manner, it ispossible to achieve the same effects as those of the magnetic sensorshown in FIG. 10 through FIG. 12.

Also, the magnetic bias film 11 described in the second embodiment ofthe invention, that is, the one in which plural magnetized magneticlayers 12 and non-magnetic layers 13 are laminated alternately, may beused as the first magnetic bias film 24 and the second magnetic biasfilm 25. In this case, because the magnetic bias film 11 has the effectsas described in the second embodiment, there can be achieved an effectthat the magnetic sensor according to the fourth embodiment of theinvention can be also reduced in size due to these effects.

The first and second magnetic bias films 24 and 25 may be the magneticbias films described in the first embodiment of the invention, that is,the one formed by arraying plural magnetic bias magnets 9A through 9G,each of which is in the shape of substantially a rectangular prismhaving the long side, the short side, and the thickness in order ofdecreasing lengths and generates a magnetic field, in the short sidedirection while aligning the directions of the magnetic fields.

This magnetic sensor can obtain a stable magnetic bias because itincludes the first and second magnetic bias films 24 and 25 that use themagnetic bias film 9 formed by arraying plural magnetic bias magnets 9Athrough 9G, each of which has an aspect ratio of the long side and theshort side set in a range of 5 to 200, in the short side direction whilealigning the directions of the magnetic fields. It is thus possible toobtain a magnetic sensor with which properties of the magnetic fieldremain stable against a magnetic field from the outside.

Fifth Embodiment

FIG. 17 is a cross section of a magnetic sensor according to a fifthembodiment of the invention. For the magnetic sensor according to thefifth embodiment of the invention, like components are labeled with likereference numerals with respect to the magnetic sensor according to thefourth embodiment of the invention described above, and only differenceswill be described herein.

That is to say, differences of the magnetic sensor according to thefifth embodiment of the invention from the magnetic sensor according tothe fourth embodiment of the invention are as follows. In the magneticsensor according to the fourth embodiment of the invention describedabove, the first magnetic detection portion 21 and the second magneticdetection portion 22 are formed directly on the top surface of thesubstrate 20. On the contrary, in the magnetic sensor according to thefifth embodiment of the invention, the first magnetic bias film 24 andthe second magnetic bias film 25 are formed directly on the top surfaceof the substrate 20. Even when configured in this manner, it is possibleto achieve the same effects as those of the magnetic sensor according tothe fourth embodiment of the invention described above.

It should be appreciated, however, that the magnetic sensor of theinvention is not limited to the contents described in the fourth andfifth embodiments of the invention described above.

For example, the fourth and fifth embodiments of the invention describedabove adopt the method of detecting a differential output voltage byemploying the Wheatstone bridge circuit using four magnetic detectingelements as each of the first magnetic detection portion 21 and thesecond magnetic detection portion 22. However, a method using a halfbridge circuit configuration employing two magnetic detecting elementsmay be adopted. This will be described using FIG. 18.

FIG. 18 is a circuit diagram showing a modification of a magneticdetection portion in the magnetic sensor according to the fifthembodiment of the invention. As is shown in FIG. 18, the first magneticdetection portion 21 comprises a first magnetic detecting element 27Aand a second magnetic detecting element 27B, and it detects a voltagebetween the first output electrode 30A and the first ground electrode29A by applying a specific voltage between the first input electrode 28Aand the first ground electrode 29A. This circuit configuration isreferred to as the half bridge circuit because it has half theconfiguration of the Wheatstone bridge circuit. Also, the secondmagnetic detection portion 22 is configured in the same manner as thefirst magnetic detection portion 21.

In comparison with the Wheatstone bridge circuit, the half bridgecircuit configuration described above has a simpler circuitconfiguration, because it requires half the number of detecting elementsand an area needed for the circuit can be smaller, and is thereforeadvantageous in achieving a size reduction.

Other Embodiments

(A) The fourth and fifth embodiments of the invention described themagnetic sensor serving as an orientation sensor. The invention,however, is not limited to these embodiments, and the invention is alsoapplicable to other magnetic sensors using magnetic biases. For example,the invention is useful as a compact sensor that detects a particularlyfaint magnetic field, such as a magneto impedance effect element.

(B) In the embodiments of the invention, the magnetic bias magnets 9Athrough 9G in the first embodiment, the magnetic layers 12 in the secondand third embodiments were described as those made of CoPt alloy.However, they may be made of other alloys, such as CoCr alloy and CoCrPtalloy, or ferrite magnet. In particular, as with CoPt alloy, CoCr alloyand CoCrPt alloy have large magnetocrystalline anisotropy in addition toan excellent magnet property. They are therefore suitable as a materialof a magnetic bias magnet to which the stability of the magnetic fielddirection is required.

(C) The embodiments of the invention described a case where theinsulation layer is made of SiO₂. However, the insulation layer may bemade of other materials, such as alumina, epoxy resin, and siliconresin.

(D) The embodiments of the invention described a case where CoPt alloyto be used as the magnetic layers 12 is formed by means of vapordeposition or sputtering. However, the CoPt film may be formed by othermethods, for example, by applying a CoPt precursor by a wet methodfollowed by sintering.

(E) The embodiments of the invention described a case where thedirection of the magnetic field of the magnetic bias film 11 isstabilized by applying manufacturing or adopting the laminatedstructure. However, besides these cases, a method by which a magneticfield in one direction is applied using a magnet or the like when themagnetic bias film 11 is formed (film deposition with magnetic field),and a method by which heat treatment is applied at a specifictemperature while applying a magnetic field in one direction after themagnetic bias film 11 is formed (heat treatment with magnetic field) areincluded as means for actively providing such anisotropy in onedirection (uniaxial anisotropy). The anisotropy provided by the filmdeposition with magnetic field and the heat treatment with magneticfield is normally referred to as induced magnetic anisotropy.

Further, available methods include means for providing uniaxialanisotropy to the magnetic bias film 11 using a counter result ofmagnetic strain, that is, by applying a stress while the magnetic biasfilm 11 is formed.

In this embodiment, too, it is preferable to provide magnetic anisotropyto the magnetic bias film 11 using these methods, because the biasmagnetic field can be more stable.

(F) In the embodiments of the invention, the magnetic detecting elementswere described as a ferromagnetic thin film including NiCo or NiFeserving as a magneto resistance film or an artificial latticedmulti-layer film. However, besides these, they may be InSb or InAs,which are semiconductors having a large electron mobility and known toexhibit the magneto resistance effect.

While the invention has been described in detail, the descriptions aboveare illustrative in all aspects and the invention is not limited tothese descriptions. It is therefore understood that a large number ofmodifications that are not described herein can be anticipated withoutdeviating from the scope of the invention.

INDUSTRIAL APPLICABILITY

The magnetic bias film of the invention is able to generate a stable andstrong magnetic field within a plane perpendicular to the laminationdirection of the magnetic layers. Because the magnetic bias film can bereduced in size and suitable for use in a magnetic sensor, it isindustrially useful.

1. A magnetic bias film including plural magnetic bias magnets eachhaving magnetic layers and generating a magnetic field within a planeperpendicular to a lamination direction of the magnetic layers, wherein:the magnetic bias magnets is manufactured in a shape of substantially arectangular prism having long sides, short sides, and a thickness in thelamination direction in order of decreasing lengths while a ratio of thelong sides with respect to the short sides in length is in a range of 5to 200, and the plural magnetic bias magnets are disposed in a shortside direction.
 2. The magnetic bias film according to claim 1, wherein:the magnetic bias magnet further includes a non-magnetic layer, and twoor more magnetic layers and one or two or more non-magnetic layers arelaminated alternately.
 3. The magnetic bias film according to claim 2,wherein: the non-magnetic layer is made of one of Cr, Ti, Cu, Al, Sn,Nb, Au, Ag, Ta, and W.
 4. The magnetic bias film according to claim 2,wherein: a thickness of the non-magnetic layer is in a range of 50 Å to500 Å.
 5. The magnetic bias film according to claim 1, wherein: adirection of the magnetic field generated by the magnetic bias magnet isin a long side direction.
 6. The magnetic bias film according to claim2, wherein: a direction of the magnetic field generated by the magneticbias magnets is in a short side direction.
 7. The magnetic bias filmaccording to claim 1, wherein: the magnetic layers are made of one ofCoPt alloy, CoCr alloy, CoCrPt alloy, and ferrite magnet.
 8. Themagnetic bias film according to claim 1, wherein: a thickness of themagnetic layers is in a range of 250 Å to 2500 Å.
 9. The magnetic biasfilm according to claim 1, wherein: the number of the magnetic layers isan odd number.
 10. The magnetic bias film according to claim 1, wherein:strength of the generated magnetic field is 5 Oe or higher and 20 Oe orlower.
 11. The magnetic bias film according to claim 1, wherein:magnetic anisotropy is provided to the magnetic layers as the magneticlayers are formed while a magnetic field is applied in one directionwithin the plane perpendicular to the lamination direction of themagnetic layers.
 12. The magnetic bias film according to claim 1,wherein: magnetic anisotropy is provided to the magnetic layers as heattreatment is applied to the magnetic bias magnet at a specifictemperature while a magnetic field is applied in one direction withinthe plane perpendicular to the lamination direction of the magneticlayers.
 13. A magnetic sensor, comprising: a substrate; a first magneticdetection portion provided with at least two magnetic detecting elementsformed on a main surface side of the substrate; a second magneticdetection portion provided with at least two magnetic detecting elementsformed on the main surface side of the substrate; a first magnetic biasfilm provided at a position opposing the first magnetic detectionportion; and a second magnetic bias film provided at a position opposingthe second magnetic detection portion, wherein the first and secondmagnetic bias films are the magnetic bias film according to claim 1, andan orientation of a magnetic field generated by the first magnetic biasfilm and an orientation of a magnetic field generated by the secondmagnetic bias film are different.
 14. The magnetic sensor according toclaim 13, further comprising: an insulation film that covers at leastone of the first magnetic detection portion and the second magneticdetection portion.
 15. The magnetic sensor according to claim 13,wherein the first magnetic detection portion includes: a first magneticdetecting element; a second magnetic detecting element that has alongitudinal direction of a pattern different from a longitudinaldirection of a pattern of the first magnetic detecting element, and iselectrically connected to the first magnetic detecting element inseries; a third magnetic detecting element that has a longitudinaldirection of a pattern parallel to the longitudinal direction of thepattern of the second magnetic detecting element; and a fourth magneticdetecting element that has a longitudinal direction of a patternparallel to the longitudinal direction of the pattern of the firstmagnetic detecting element, and is electrically connected to the thirdmagnetic detecting element in series, the first magnetic detectingelement and the second magnetic detecting element being electricallyconnected to the third magnetic detecting element and the fourthmagnetic detecting element in parallel, and wherein the second magneticdetection portion includes: a fifth magnetic detecting element; a sixthmagnetic detecting element that has a longitudinal direction of apattern different from a longitudinal direction of a pattern of thefifth magnetic detecting element, and is electrically connected to thefifth magnetic detecting element in series; a seventh magnetic detectingelement that has a longitudinal direction of a pattern parallel to thelongitudinal direction of the pattern of the sixth magnetic detectingelement; and an eighth magnetic detecting element that has alongitudinal direction of a pattern parallel to the longitudinaldirection of the pattern of the fifth magnetic detecting element, and iselectrically connected to the seventh magnetic detecting element inseries, the fifth magnetic detecting element and the sixth magneticdetecting element being electrically connected to the seventh magneticdetecting element and the eighth magnetic detecting element in parallel.16. The magnetic sensor according to claim 15, wherein: an angleproduced by an orientation of a magnetic field generated by the firstmagnetic bias film and an orientation of a magnetic field generated bythe second magnetic bias film is 90°, an angle produced by thelongitudinal direction of the pattern of the first magnetic detectingelement and the longitudinal direction of the pattern of the secondmagnetic detecting element is 90°, and an angle produced by thelongitudinal direction of the pattern of the fifth magnetic detectingelement and the longitudinal direction of the pattern of the sixthmagnetic detecting element is 90°.
 17. The magnetic sensor according toclaim 16, wherein: an angle produced by an orientation of a magneticfield generated by the first magnetic bias film and the longitudinaldirection of the pattern of the first magnetic detecting element is 45°;and an angle produced by an orientation of a magnetic field generated bythe second magnetic bias film and the longitudinal direction of thepattern of the fifth magnetic detecting element is 45°.
 18. The magneticsensor according to claim 13, wherein the first magnetic detectionportion includes: a first magnetic detecting element; and a secondmagnetic detecting element that has a longitudinal direction of apattern different from a longitudinal direction of a pattern of thefirst magnetic detecting element, and is electrically connected to thefirst magnetic detecting element in series, and wherein the secondmagnetic detection portion includes: a third magnetic detecting element;and a fourth magnetic detecting element that has a longitudinaldirection of a pattern different from a longitudinal direction of apattern of the third magnetic detecting element, and is electricallyconnected to the third magnetic detecting element in series.
 19. Themagnetic sensor according to claim 13, wherein: the magnetic detectingelements are formed of a magnetic film including NiCo or NiFe.
 20. Themagnetic sensor according to claim 13, wherein: the insulation film ismade of SiO₂.